[imp] Can not create sub folder

[connerf]

I am using

imp version 3.2.1
horder version 2.2.3
imap-2001a-10
Redhat Linux 7.3

I can not create a sub folder.  For example I create a folder called
work and I want to create a sub folder under that called memo.  When I
click create folder I get the following error

The folder "work/memo" was not created. This is what the server said:
<i>CREATE failed: Can't create mailbox node /home/username/mail/work/:
File exists</i>

The directory $HOME/mail/work exists but $HOME/mail/work/memo does not.

Thank you